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DynaSoar writes "Scientists at the University of Chicago's Center for Astrophysical Thermonuclear Flashes have created a simulation of a white dwarf exploding into a type 1a supernova. Using 700 processors and 58,000 hours, they produced a three second movie showing the initial burst that is thought to be the source of much of the iron in the universe. Understanding these supernovas is also important to testing current cosmological theories regarding dark matter and dark energy, as their brightness is used as a measurement of distance, and discrepancies found in the brightness of very distant supernovas consistently seem to indicate a change in the speed of expansion of the universe over time."

If the 58000 hours is not cumulative, then this represents 4.6 millenia of computing time. If that were done with one processor, about 180 supernovae would explode in our galaxy during the computation.

"Though the computer simulation took a total of 58,000 hours and more than 700 computer processors, the actual process from start to finish--when the star explodes--played out in just three seconds." (Third paragraph under the subhead "Crash Code", ninth paragraph overall).

Yep, definitely nowhere in the story. Not anywhere. Definitely not in plaintext, sitting there, waiting to be read:)

I don't think the point of this story is some big feat of supercomputing. The interesting bit is that they made a really neat simulation and tossed it online. The processing power involved is a point of interest, nothing more.

THere are a lot of interesting things about this. Supernovas are believed to be a major (though not the only) source of all elements heavier than iron in the universe.

For a brief overview (based on Fowler's Nobel Prize lecture) on element formation... This is all from memory (and I am not a physicist) so do your own verification. Basically small stars burn Protium (1H). These fuse to product 2He which immediately decays into Deuterium (2H), emiting a positron. This P-P process eventually allows Deuterium to fuse forming the stable 4He.

As the amount of Helium in a star increases, it eventually becomes possible for Helium to fuse. The only problem is that 8Be is unstable and alpha decays almost immediately back into He. However, you get a small amount of 8Be sitting around for a while, and it can fuse with 4He to produce 12C (Carbon-12). From here things get interesting...

For stars with more than about 1.1 times the mass of our sun, The carbon becomes the basis for Helium production, replacing the P-P process. The basic process (called the CNO cycle) involves single captures of protons (2 of which decay into neutrons and positrons) and then the alpha decay back into 12C. In short this allows Carbon to act as a sort of catalyst for Hydrogen fusion. All elements heavier than Carbon are produced using one of a number of processes. These include fast proton capture, slow proton capture, and alpha capture. The problem is that these become endothermic at the point of Iron. So while smaller stars can produce some of the heavier elements, they are limited in the quantities they can produce. Supernovas, however, can rapidly create much larger quantities of heavier elements.

Also note that at a point in the distant past, stars were more massive than they generally are today. This means that at different points in the history of the universe, we saw large amounts of heavier elements generated.

So this is all quite interesting. I am sure at that many hours we are probably talking about a pretty detailed atomic model. The movie probably shows noting near what the simulation shows.

Does anyone else see the "face" that is created during this explosion? I see closed eyes, a nose and even a mouth(all tongue in cheek) ROFLMAO... sorry poor joke..... would love to see this at full speed.

"Supernova" is an invented word and the plural is "supernovas". Just like televisions and radios.

In fact, the word is built out of two Latin adjectives, literally it means an "abovenew". Invented words follow this rule, hence the plural of octopus is octopuses, of satellite is satellites, and of millennium is millenniums. The plural of "vertebra" is "vertebrae" because it is an actual Latin word, not an invented modern one.

Incidentally, while pursuing this very pedantic note, "satellites" is correct plural but the singular of the original word is "satelles". And the original word is pronounced sat-ell-it-ees. We are a long way from Latin.

And then there are words derived from Greek which people think are from Latin. One example is "hippopotamus", whose plural is "hippopotamuses" because it's an English word.

If anyone ever says "hippopotami", just laugh loudly at them and inform them that the correct quasi-Greek plural is either "hippopotamoi" (spoonfuls-type plural) or "hippoipotamus" (spoonsful-type plural).

Um, hi. Astronomer here (not that it matters).The word nova in the astronomical context comes from Tycho Brahe, a Danish astronomer who was writing in Latin at the time. The plural is novae, not novas. Although supernova is an English construction, the etymology is derived more directly from this Latin word than other modern inventions. Although both plural forms are strictly correct due to the artificial construction, supernovae is used predominantly in our field.

Actually, I know astronomers call them supernovae. Until recently, they also thought Pluto was a planet. Truth is, like a lot of scientists, astronomers create cod Latin and Greek for historical reasons (Latin was the common language of intellectuals, Greek was the language they used when they really didn't want to be overheard...). Unlike Tycho, they don't use either on a regular basis, and they get it wrong. Correct me if I am wrong, but Tycho called them, correctly, "new stars". The nova is an adjective,

Both could be correct if you use them properly in the sentence. Supernovae when it's the subject, supernovas when it's the object. Assuming we're treating "supernova" as a regular 1st-declension latin feminine noun.Strictly speaking, super (as a preposition of space or location, in this case) takes nova in the ablative case, so the ending on nova is a long a (ahhhhh). If we were writing in Latin I don't know that we'd use the -ae ending for the plural at all. In fact, I'm not sure what the plural would be.

"they produced a three second movie showing the initial burst that is thought to be the source of much of the iron in the universe"

Bob: But we'll never get funding with a three second image. This thing had to have caused something useful..
Joe: Well, um... how about something specific like Kevin Federline?
Bob: No, panders too much to popular culture.
Joe: That's too bad because my next thought was heavy metal music. Oh, how about some type of boring "metal" like iron ore. It's in some vitamins too which will interest the average consumer.
Bob: That'll do. We have to get the funding proposal out by noon.

Bob: But we'll never get funding with a three second image. This thing had to have caused something useful..

Didn't Janet Jackson have a star for that nipple ring thing during the Superbowl kerfluffle? If I remember right, that was 3 seconds or less. If you can get that performance out of a simulation, I guarantee someone, somewhere will give you funding. Then you just have to ask yourself if you want that money...

...but why do these people persist in blowing so much time and effort and money on stuff like this when there are far more deserving and serious problems to be solved right here and now on good old earth. Hell, we can't even tame hydrogen --> helium let alone oxygen --> iron or whatever it is. Good, solid science for sure, but the priorities seem to be way, way wrong if you ask me.

The priorities are NOT wrong!Knowledge for knowledge's sake ALWAYS ends up paying off.

Just because we dont know how to make our lives better by virtue of gaining this knowledge now, there's no reason to suppose we'll never know (in fact, history indicates that eventually ALL research pays off to some extent).

If you RTFA and do a slight bit of reasoning (I know, I know, but try), you will see that this research directly helps us understand more of the hydrogen -> helium mechanincs.

Repeat after me:ALL KNOWLEDGE IS VALUABLE.KNOWING IS ALWAYS BETTER THAN NOT KNOWING.

You got some answers which are good enough, but I'd like to add a point.Further development in materials and energy sources today relies upon gaining a better understanding of the physics involved. After all, it's hard to do engineering when you don't know the rules. While we have very good models for large-scale physics, we're still lacking at the subatomic level.

The difficulty of subatomic physics is that the particles are so small that their influences are difficult to detect. One way to solve that is

OK. I'm happy now. Part of my motivation for the original post was the irritation of seeing projects with real worth being refused funding, and at the same time someone in the Arts being given a buttload of money by the same government so they can work out some new dance steps or whatever.

Gah that article is awful. They link to pretty pictures and blurbs mostly and never really explain what these things are, why they are important or give you any real sense of scale. So since I like to beat on the drum of better communication of science, here is a little more detail to add to the good einhverfr's post.

The progenitors of SNIa are most likely white dwarfs composed of carbon nitrogen and oxygen, probably with a companion star from which they are stripping matter. They are very compact on the order of a few thousand kilometers at most, and really dense - more than the mass of the sun. They aren't hot enough to support fusion - they are supported by Pauli pressure; quantum mechanics doesn't allow two electrons in the same state at the same time so though gravity tries to compact these objects there is a Pauli pressure outward to balance it.

This can't go on forever in these progenitor systems however, and if the white dwarf strips enough matter of its companion to get to ~1.4 solar masses (the Chandrashekar limit) then Pauli pressure isn't strong enough to balance gravity and the star begins to collapse and when that happens pressure and temperature rises and somewhere a nuclear fusion flame ignites. Details about what happens near collapse, and where and how the flame ignites, and how many there are and how they progress are still debated. In this particular model they are considering only a single flame (so far) and its a "gravitationally confined detonation" (GCD - the name of this particular model).

Its a little difficult to get a sense of scale from those videos, though there are numbers in the bottom corner. The flame starts of near or just of center and becomes bubble/mushroom shaped through a Rayleigh-Taylor instability [wikipedia.org] and breaks the stellar surface in under a second. Its less than another second before the ash and flame from the bubble collides at the opposite end of the star. This flame crashing into itself (see video 1) causes compression and a detonation.

Theres been a lot of debate as to whether its a deflagration or a detonation or whether it transitions from one to the other and how and when that happens and us poor graduate students just hope they don't go crazy over details of the progenitors during our qualifying examinations. This is notable because there appears to be a growing number of voices who are saying that a detonation is necessary. These events are so standard because they all become SNIa if they get near 1.4 solar masses. There is a fair bit of diversity (and some just crazy objects) and most of that probably arises from details during the explosion which is why modeling them is partly why the models are so important.

There is still a lot of modeling left to do. This flame is producing a lot of heavy elements (there is O, S, Ca, Mg and Si in the early spectra - the silicon feature is around 6150 angstrom in the rest frame and is the marker of a Ia at low to moderate redshifts). As the outer layers expand and become more transparent you see more of the material produced during the explosion and a lot of this is Nickel (Ni-56) which decays to cobalt and powers the light curve so you get this typically 2 week rise and then a slow fall off. Later times most of the Ni has become cobalt which is decaying to iron and you see these elements in the spectrum. The energies we are talking about here are about 10^45 Joules. A H bomb by contrast is 10^15 Joules so 30 order of magnitude. Unless you can picture 10^30 H bombs going off its hard to get a feeling for this number but thats generally the case with numbers in cosmology.

There are a lot of empirical relations you see from the lightcurve, which are exploited to standardize them (for instance the brighter the supernova, the slower its rate of decline, and there are relations for the colour...) and if a model can replicate them and match the observed lightcurves and spectra then this is a very impressive accomplishment. I skim

Its a little difficult to get a sense of scale from those videos, though there are numbers in the bottom corner. The flame starts of near or just of center and becomes bubble/mushroom shaped through a Rayleigh-Taylor instability and breaks the stellar surface in under a second. Its less than another second before the ash and flame from the bubble collides at the opposite end of the star. This flame crashing into itself (see video 1) causes compression and a detonation.

I don't get it. The flame expands outward to the surface in less than a second. I am ok so far. Now to do that the material would need to have a lot of momentum in the direction it is going, so how does it suddenly turn around and crash into itself on the other side? Not by gravity, or? Is there a pressure wave caused by the flame that travels along the surface and meets with itself on the other side, causing increased pressure and detonation as a result?

I don't get it. The flame expands outward to the surface in less than a second. I am ok so far. Now to do that the material would need to have a lot of momentum in the direction it is going, so how does it suddenly turn around and crash into itself on the other side?>

It is not the material itself that 'turns around', but rather the gas/plasma pressure increase that propagates (at nearly relativistic speeds, no less. The simulated star was earth-sized; imagine traveling to the other side of our planet

I hate to state the obvious but we would go looking for them and if we didn't find them, we would go "back to the drawing board". It's science 101...

1. Observe.

2. Model.

3. Predict.

4. Repeat.

Science is littered with dead models, not to put too fine a point on it but that's how it works. The only belief required says that "the real world exists as something seperate from the internal model created by my brain, commonly called p

We need to keep the scientific method in mind anytime we read a study. Far too many people are willing to take a study as an absolute truth instead of a new way of seeing an incident. This coupled with the fact that too many people already have a problem with the concept of a law and a theory makes talking about science in a meaningful way fairly hard.

So yes, there is tons to be discovered even in our own backyard but at the same time theories and predictions can be mad

So yes, there is tons to be discovered even in our own backyard but at the same time theories and predictions can be made with some degree on without knowing everything there is to know.

I accept your logic. But you fall short of describing the complete scientific method. If you make assumptions, and then make additional observations that tend to disconfirm your assumptions, then there are times when your discoveries should cause you to re-examine your initial assumptions. We've launched all sorts of prob

It's a constant process of doubting your own arguments though. In this particular case, I screwed up a little bit because 1987A is categorized as a Type II supernova, which is not used as a standard candle. Type 1a supernovae are used for standard candles.One of the difficult things in thinking about the arguments on both sides is merely keeping track of all of the categorization that has been created to accomodate the observations to the Big Bang and stellar evolution theories. Traditional theories tend

I wanted to add one more thing to my previous response.What's happening right now with astrophysics is extraordinary. It's never been the case to my knowledge that modern man has been so wrong about something and simultaneously so confident in his wrong beliefs. The implications can potentially be catastrophic in the long-term. But there is a little-mentioned business side to this story. The EU Theorists have done a great job of laying down the groundwork for some possibly lucrative financial ventures.

You can reach me directly at pln2bz@vireo.net. I don't mind posting my email address. To be honest, nobody on this forum really cares what I think. And I don't care that they know what I'm doing.There is nobody currently focusing on the educational system, believe it or not -- not since Hannes Alfven at least, who died more than a decade ago. Hannes Alfven was smart in that he left many descendants of his inquisitive philosophy. You can run into these guys all over the place on the web. The best thing

I agree, (type II) supernovae actually destroy their iron core in order to create heavier nuclei from the new, neutron-rich environment.Here's a link:http://www.daviddarling.info/encyclopedia/R/r-proc ess.html [daviddarling.info] Here, they are simulating a type I supernova: a white dwarf that 'steals' mass from its neighbor until it reaches some critical mass, and we see a supernova.

What's fascinating to me is the behavior of the explosion front. At first it seems counterintuitive for it to 'burrow' towards the surface and burst asymetrically. But when you stop and think about it, that is the behavior you should expect - the expansion is the direction of least resistance, into regions of lower pressure.